Tech makes dirty water drinkable — with a little help from carbon dioxide

Virtually everyone reading this article takes clean drinking water for granted. But that is not the case throughout the world, where hundreds of millions of people lack access to the necessary kind of water treatment tools that can make it safe to drink.

In a new research project, investigators from Princeton University, Unilever, and the University of Hawaii describe a new method of making water drinkable — by counterintuitively mixing it with carbon dioxide, which is normally considered a pollutant.

“We have used a CO2 gas as a means to remove suspended particles,” Sangwoo Shin, an assistant professor of Mechanical Engineering at the University aof Hawaii at Manoa, told Digital Trends. “When CO2 is in contact with water, it dissociates into ions, which subsequently generates a small electricity. Yet, this electricity is big enough to push the suspended particles. We use this principle to achieve efficient, continuous, scalable water filtration that does not involve any porous filters.”

The idea of taking a cup of water from a contaminated pond or river and then blasting it through with pressurized carbon dioxide to get a fresh cup of drinking water sounds impossible, but that is exactly what Shin says the group’s research can achieve. “Imagine a small CO2 tank that goes with a paintball gun or soda stream,” he said, describing the source of the pressurized CO2. He notes that the technology could also be used for military purposes, in which soldiers are not guaranteed a clean source of drinking water.

In tests, the system was shown to be capable of removing all but 0.0005 percent of target particles and doing so with less than 1/1,000 of the energy a membrane filtration system would require.

“Our demonstration is still immature at the moment and limited to a lab scale test,” Shin continued. “There are many engineering design factors to be considered for a possible commercialization, including scaling-up and optimization for use in households or water treatment plants to supply larger communities. We are hoping to see a large-scale water filtration device in the near future.”